In recent years, a disk array apparatus which combines a plurality of disk apparatuses such as a magnetic disk apparatus or an optical disk apparatus has been used widely as demand for storing data has been more increasing. The disk array apparatus processes I/O (Input/Output) instructions issued from a plurality of upper level apparatuses simultaneously. Moreover, the disk array apparatus processes a plurality of instructions to a plurality of disk apparatuses simultaneously.
It is desirable that the disk array apparatus is always working since it is necessary for the disk array apparatus to memorize and store a large amount of data. However, it is necessary in some cases to exchange firmware, which is working practically on the disk array apparatus, in order to debug the firmware or to get rid of a security hole.
As a related art on firmware of the disk array apparatus, and in particular on exchange of firmware, following documents, for example, are disclosed. Japanese Patent Application Laid-Open No. 2000-215042 (patent document 1) discloses technology that firmware for update is stored in a standby plane of a memory in advance and an address conversion apparatus converts an apparent address. According to the technology disclosed in the patent document 1, the firmware is exchanged without stopping a computer system. Japanese Patent Application Laid-Open No. 2006-031312 (U.S. counterpart application thereof is US 2006/0015861A1) (patent document 2) discloses a computer system which includes a plurality of blades. According to the patent document 2, one blade, which includes firmware to be exchanged, transfers service to other blade. Afterward, the blade is shut down and then, the firmware is exchanged.
Japanese Patent Application Laid-Open No. 2006-260395 (patent document 3) discloses a program loading method with which a program is assigned to virtual space and loaded into a physical memory. Japanese Patent Application Laid-Open No. 2006-338217 (patent document 4) discloses a storage apparatus each of whose modules has a plurality of CPUs (Central Processing Units) and firmware. Specifically, the patent document 4 discloses technology that a process of each module is concentrated at one CPU of the module and other CPU exchanges firmware during the concentration time. Japanese Patent Application Laid-Open No. 1999-237957 (U.S. counterpart application thereof is U.S. Pat. No. 6,240,470B1) (patent document 5) exemplifies technology that necessary data are evacuated and then, firmware is exchanged, as technology of hot standby exchange of firmware.